Powertrim release valve stuck

[Jomce]

Yamaha 1996 40 VETOL powertrim motorcap rusted motor now dead and has to be changed.

O-snap taken out from front of manual release-screw, wich won´t turn right or left - at all.

Arrow on bracket suggests counterclockwise unscrewing. Is this so or perhaps a lefthanded screw?

Suggestions:
Drilling away?
Using directblow releaser
Other means known to solve the problem?

Anything to be aware about lifting the motor off
related to hydraulic pressure in the powertrim?

Best regards

[boats.net]

The arrow on bracket is showing the direction to unscrew manual release and to allow to tilt motor by hand. If it want unscrew you might try to use a hammer impact wrench to break loose, usually works.